Add Two Numbers

https://leetcode.com/problems/add-two-numbers/description/

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
给定两个非空链表，表示两个非负整数。这些数字以相反的顺序存储，每个节点都包含一个数字。添加两个数字并将其作为一个链表返回。

You may assume the two numbers do not contain any leading zero, except the number 0 itself.
你可以假设这两个数字不包含任何前导零，除了数字0本身。

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        int n = l1->val+l2->val;
        ListNode *head = new ListNode(n%10);
        ListNode *tmp = head;
        l1 = l1->next;
        l2 = l2->next;
        
        while((l1) && (l2)){
            n = n/10;
            n = n + l1->val + l2->val;
            tmp->next = new ListNode(n%10);
            tmp = tmp->next;
            l1 = l1->next;
            l2 = l2->next;
        }
        while((l1)){
            n = n/10;
            n += l1->val;
            tmp->next = new ListNode(n%10);
            tmp = tmp->next;
            l1=l1->next;
        }
        while((l2)){
            n = n/10;
            n += l2->val;
            tmp->next = new ListNode(n%10);
            tmp = tmp->next;
            l2=l2->next;
        }
        if (n/=10){
            tmp->next = new ListNode(n);
        }

        return head;
    }
};